Police are investigating the possibility that a nine-year-old boy who drowned in a river in southern Brazil was playing Pokemon Go at the time and said they would sue the maker of the popular mobile game if that were the case.

Police are investigating the possibility that a nine-year-old boy who drowned in a river in southern Brazil was playing Pokemon Go at the time and said they would sue the maker of the popular mobile game if that were the case.

Two nine-year-old boys were playing on rowing boats on Monday and one fell into the river and drowned, a police statement said.

Media reports said the boys were hunting Pokemon characters, a version of events that was included in an initial military police report.

Parents of the boys, however, denied they were playing Pokemon Go and said the Alcatel One Touch phone belonging to the surviving child did not have the app installed on it.

But police have not ruled out that the game could have been linked to the drowning.

"The smartphone we seized today does not have the app for the game. We are investigating whether or not it had been installed," said Antônio Carlos Ractz, chief of the civilian police in the town of Imbé, Rio Grande do Sul state.

"If it was there, we'll study legal action against the app's maker, because it has no age restrictions and has already caused accidents the world over," Ractz said by telephone.

Representatives for game developer Niantic and Nintendo Co could not immediately be reached for comment.

Pokemon Go uses augmented reality and Google mapping to make animated characters appear in the real world. Players see creatures overlaid on the nearby landscape that they see through a mobile phone camera.

The game has prompted safety warnings after players glued to their phones stumbled, were robbed or wandered into dangerous places. The app has been downloaded more than 100 million times, according to analytics company App Annie.

Nintendo, which owns a large stake in the game's publisher, The Pokemon Company, has seen its stock price surge after the success of Pokemon Go.